Producing aluminum oxid from sulfate of alumina.



G. SCHWAHN. PRODUGING ALUMINUM OXID FROM SULFA'IE 0F ALUMINAyAPPLICATION FILED DEC.12, 1908.

Patented Mar. 23, 1915.

3 SHEETS-'SHEET l.

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Inventor:

Witnes se s:

G. SCHWAHN.

PRODUCING ALUMINUM OXID PROM SULPATE 0F ALUMINA.

APPLICATION FILED DBC.12, 1908.

Patented Mar. 23. i9 1 3 SHEETSfSHEE'I 3 Winesses:

G. SGHVVAHN.

` PRODUCING ALUMINUM OXID FROM SULPATE of ALUMINA.

APPLICATION YILED DE!4 12, 19025 Patented Mar. 23, 1S) 1 SSHEETS'SHEET 3Fig. 10.

Inventor:

Witnesses:

GUSTAVE SCHWAHN, OF BELLEVILLE, ILLINOIS.

PRODUCING ALUMINUM OXID FROM SULFATE 0F ALUMINA.

.specification of Letters Patent.

Patented Mar. 23, 1915.

Application led December 12, 1908. Serial No. 467,155.

T o all whom it may concern Be it known that I,'GUSTAVE SCHWAHN, acitizen of the United States, and resident of the city of Belleville, inthe county of St. Clair and State of Illinois, have invented certain newandL useful Improvements in Producing Aluminum Oxid from Sulfate ofAlumina, of which the following is an exact specification.

This invention relates to the production from aluminum sulfate of theoxid of aluminum (alumina), suitable for electrolytic reduction toaluminum. While sulfuric acid combines with aluminum in severalproportions, the sulfate of aluminum that I have in view as the mostdesirable for my purposes may be represented by the formula A1,(SO4) 3,that is, dehydrated ory calcined normal sulfate of aluminum. Thismaterial I subject to adequate heat and steam to drive off the acid indissociated form, substantially as hereinafter more fully described andclaimed.

It is known that by subjecting incandescent aluminum sulfate to theaction of hydrogen gas the sulfate is decomposed, forming water andsulfur dioxid, and leaving alumina nearly free of acid. Such a processis however, not commercially operative, at the present day, as theproduction of hydrogen gas is too 'expensive The use of water gas, whichcontains free hydrogen, does not permit the production of alumina freeboth of sulfur and of. aluminum compounds containing sulfur and carbon,which are objectionable in the reduction of alumina to metal byelectrolysis from a bath of fused Huorids as practised at the presenttime, and moreover, water-gas is also too expensive.

In my improved process I use steam or aqueous vapors to act upon heatedanhyldrous aluminum sulfate, and separate the facid and impurities fromthe cetitained alumina, the alumina thus obtain 'being entirely freefrom acid and the impurities lerened in amount.

In the accompanying drawings, which form part of this specification, and'wherein like symbols refer to like parts wherever thesymbols'occur,-Figure 1 is a plan View of the type of furnace preferablyused in applying my process; Fig. 2 is' a-vertical cross section of thefurnace on the line 2 -2 of Fig. 1, looking in the direction indicatedby the arrows corresponding to the line 2 2,

Fig. 1; Fig. 3 is a vertical lbngitudinal sectlon on the line 3-3 ofFig. 1, looking in the direction indicated by the arrows correspondlngto the line 3 3, Fig. 1; F ig. 4 is a longitudinal section on the line2-2 of Fig. 1 of a device for supplying gas or vapor to the retort,which forms part of the furnace, andlfor discharging the retort; Fig. 5is a vertlcal longitudinal section of a modified form of furnace, whichmay be used in applying my process; Fig. 6 is a cross section of thesaid furnace on the line 6-6 of Fig. 5, looking in the directionindicated by the arrows corresponding to thih line 6 6, Fig. 5; F 1g. 7is a detail of the said furnace; Fig. 8 is a vertical longitudinalsection of a modified form of furnace, which may be usedin applying myprocess; Fig. 9 is a cross section of the said furnace on the line 9-9of Fig. 8, looking in the direction indicated by the arrowscorresponding to the line 9-9 of Fig. 8; Fig. 10 is a verticallongitudinal section of a modified form of furnace which may be used 1napplying my process; Fig. 11 1s a cross section of the said furnace onthe line 11-11 of Fig. 10, looking in the direction indicated by thearrows corresponding to the line 11-11, Fig. 10; Fig. 12 is a verticallongitudinal section of a modified form of furnace, which may be used inapplyingl my process; Fig. 13 is a cross section ofthe said furnace onthe line 13-13 of Fig. 12, looking in the direction indicated by thearrows corresponding to the line 13--13, Fig. 12; and Fig. 14 is adetail of the said furnace.'

In carrying out my invention, I preferi ably use a suitable retort Awithin a suitable furnace B, in the apparatus shown in Figs. 1 to 1.AThe retort isl constructed of fire brick or other material capable ofresisting temperatures up to 1200 degrees centigrade and is separatefro\1jn the furnace. The inside of the retort measures not over eightinches in width, and preferably about eight fe'et or more in height.'The furnace B s'liown in the drawings is intended to be* heated withgas, which enters the furnaceB by the pipes C which convey the gas tothe upper portion of the combustion chamber Air, which maybe preheated,is also conveyed into the upperl portion of the combustion chamber D bypipes E. The products of combustion leave the lower portion of thecombustion chamber D through 'pas- 110 sages F connecting the combustionchamber` D with a flue G. Material may be fed into the upper part of theretort A from a hopper H by means of a feeding device I, which issubstantially gas tight. rfhe hopper H and feeding device I may compriseconnections for a pipe or pipes J, which connect with the retort A belowthe feeding device I. These pipes J convey the gaseous products awayfrom the retort. The solid product of the retort may be discharged bymeans of a device K, comprising a bod v portion L, which is divided intotwo parts. The upper part M comprises a feeding device N, which byrevolving` causes the contents o the retort to pass through perforationsO connecting the upper part ).I of the discharging device K to the lowerpart P. The lower part P of the discharging device K, in connection witha screw Q, forms a screw conveyer, by means of which the solid productsof the retort may be conL veyed away from the furnace. The upper portionM of the dischargingr device K con tains a pipe or pipes R comprisingperforations S. These pipes R convey gases or vapors into the retort.into such retort.. after heating; it to an adequate temperature, whichmay be about orange red or orange heat, charge! the anhvdrfus aluminumsulfate, which is preferabl.. -n the. form of a porous mass, through thefeeding device provided therefor in its upper part or top. As soon asthe charge is heated to incandescence I introduce steam or vater in modicrate amounts into the lower part of the retort, where it becomesheated, whereby steam, or the aqueous vapors resultant from heating thewater, will be brought. into coutact with the incandescent aiuminum sulfate. This vapor is then in such condition. and under such pressure asto permeate. through and act upon the porous aluminum sulfate,liberating the acid. The water vapor in this condition and theincandescent porous sulfate coming in intimate contact, formsulfur-oxygen compounds and water, which pass off as gases. Thesesulfur-ox)YA gen compounds may be collected and suitably treated to Formsulfuric acid for the production of more sulfate.

The alumina, entirely freed from the acid, is discharged at the bottomof the apparatus by means of the device shown, or other suitable means.The process may be carricd on in a continuous operation by charging thesulfate from above as fast as the alumina is taken out from below.

The continuous method of operation pre.- sents many advantages inpractice. The column of aluminum sulfate may bc progressively advancedthrough the furnace against the moving current of vapor in such a mannerthat the. very hot, nearly sulfurfree alumina first contacts with thefresh water vapor which, of course, will be free., or substantially so,of sulfur compounds and will exercise its maximum effect. In thiscontinuous manner of operation, any convenient form of apparatus may beemployed; any apparatus which will permit the continuous progression ofa column or layer of sulfate of alumina in the contrary direction to acurrent of water vapor which may be highly superheated. Heating meansmust of course be provided which will allow of the production andmaintenance of uniform temperatures and temperature grada` tions in allparts of the apparatus.

In the apparatus shown in Figs. 5, 6 and T, a furnace i having,r ageneral cylindrical forni is mounted on rollers b, so that it may herevolved about thc axis of the cylinder ibi" any o Aitable means. Thefurnace a. coma prises two chambers c and d through the outer nner ofwhich the material tobe treated passes. This outer chambercis formed byatube r comprising suitable rcfra .tor \v material forming the outer wallot' the furnace and the inner tubo forming the inner wall of the saidouter chamber c and the second chamber. which is a combustion chamber g.'i ie outer chamber or space c for the material is made narrow. Thegases for coinbustion cuter the combustion chamber from a tube li.combustion chamber through a suitable opening or openings i. Neither thetube z. conveying gas to the. furnace, nor the stark j comes in directcontact with the revolving portion of the furnace. Gas or vapor issupplied to the outer chamber c from a tube lr, a portion ot' which l,com prisiufr a swivel joint m, is concentric with the cylindricalfurnace a. A second tube n, a portion of which o, comprising,r a swiveljoint p, concentric with the cylindrical fuinacc a, is connected withone end q of the furnace a. The furnace is revolved so that the materialis carried through it by gravity. suitable bent tube 1- with a hingedcover Air for combustion enters thel s, which opens by a pin t strikinga portion u thereof and overcoming,r the pressure of the spring,r if,picks up the material to be treated w from a suitable receptacle :v anddrops it into the outer chamber c. The niaterial leaves the furnace c bvthe tube n leadingr io an acid chamber, being carried into thc said tuben by =ases passing through the outer chamber c and by the revolvingaction of the furnace and b v `gravity. The stationary portion of thishercinl'iefore mentioned second tube n connected with one end r] of thefurnace comprises a branch y which extends downwardly and is open atthe. lower end. The material drops through this branch into a suitablereceptacle e.

The cylindrical furnace, Figs. il and 7, hereinbcforc described7 may bemodified by carrying the gas and, air for combustion -t-o sis f thecombustion chamber A', Figs. 8 and 9,

by a suitable tube B' and through a suitable openin C' to the lower endD of the furnace E and carrying away the products of combustion througha suitable tube F' connecting with the upper end G' of the furnace. Thematerial chamber H' is made the inner chamber H' in place of the outerchamber. In this case the space for the material ma be made narrow byplacing a lcylindrical evice I' of suitable refractory Yivnaterial inthe said inner chamber 'H'. The hopper or receptacle J' for the materialmay be C Osed by a suitable cover K'.

The axes of the revolving furnaces hereinbefore described may be made soas to incline at a small angle with a vertical line inplace of ahorizontal line. Figs. 10 and 1'1 rshow a furnace of this kind. In thisfurnace L a series of low cylindrical chambers J M connected by suitablepassageways N', O' form the combustion chamber 1),and a similar seriesof chambers Q' forni the material chamber rR. The assageways S', T', connecting the series of) low cylindrical material chambers Q are madesmall so as to bring gas or vapor in intimate contact with all thematerial. Each passageway S that permits the material to drop into anyone low cylin dricul chamber Q' is placed diametrically opposite thepassageway T that permits the material to drop to the next lowerchamber, so' that as the material passes through the f lrnace thematerial must pass through each chamber Q.' in succession. Thesuccessive psageways N', O' connecting the low cylindrical combustionchambers M' are similarly located with respect to each other. The

vlowest passageway U for gas and air and .the uppermost passageway V forproducts of combustion are concentric with the axis of the cylindricalfurnace. The top W' of the furnace to which the material supply pipe Xand the pipe Y' to the acid chamber are connected isstationary and formsa hood Z with respect to the revolving furnace L'. The cover A" of thereceptacle for treated materials swivels with respect to the saidreceptacle. The gas or vapor pipe B enters the said receptacle.

In carrying out my invention the material may be Amade to passthroughthe chamber in which the combustion takes place. Figs. 12, 13 and 14show a revolving cylindrical furnace of this kind. The material entersthe furnace a through a fixed pipe b' moves along the bottoni of thecombustion chamber c in a thin layer and leaves the furnace by a smallpipe d' attached to and revolving with the furnace a'. The gas or vaporenters the furnace a' through a pipe e' comprising a swivel joint f'concentric with the revolving furnace c'. This swivel joint f'conipnises a fixed portion g' and a revolving portion h' with fourpassageways i', so

placed as to form a fourway valve. The

passageway j' in the fixed portion g of this device is so placed that itconnects with each of the four passageways z" in the revolving portionh' in succession, when one of the said passageways i connecting withthat one of the four pipes le' placed in the furnace lining and having aseries of openings l' into the furnace a' is in its lowest positionduring each revolution. Gas or vapor consequently enters the lowestportion of the cylinder only and comes in direct contact with thematerial. The four hereinbefore mentioned gas or vapor pipes t" are notas long as the combustion chamber c'. The material is consequentlyheated before it comes in Contact with the gas or vapor.

An important advantage of my process is that with the separation of theacid from the aluminum sulfate and the setting free of the c' alumina,the alumina is also partly, if not Wholly, freed from all impurities,such as iron, titanic acid or even silica, which may have been containedin the sulfate. It is not essential to a successful operation of thepresent process that the sulfate be in a porous condition or that thesteam supplied to the furnace be in supcrheated condition.

Vilhile I consider the furnace illustrated in Figs. 1 to 4 to be bestadapted to cour mercial production of alumina from aluminum sulfate bymy process, my process is not restricted to the use of this furnace.

The rotary furnaces shown in Figs. 5 to l 14, or any furnace adapted toaccomplish the uniform heating of the sulfate and intimate admixture ofthe water vapor therewith, substantially as described, may be used.

No claim is made herein for the furnace constructions shown in theaccompanying drawings and described above, but the new and usefulfeatures thereof are expressly reserved for a future application forLetters Patent. 4

I claim as new, and as my invention:

l. -The production of aluminum oxid from aluminum sulfate by means whichconsists in charging anhydrous aluminum sulfate in a` porous conditioninto a retort in a furnace, heating said sulfate to incandescencethroughout, and then charging water, aqueous vapors or steam into saidretort while maintaining the sulfate at a uniform teniperature until allthe sulfuric acid is removed, substantially as described.

2. The improved processf of producing aluminum oxid, which consists insubjecting porous aluminum sulfate inthe presence of aqueous vapors orsteam to about an orange' red or orange heat, substanti ally as and forthe purpose set forth.

part of a chamber of a suitable retort or furnace, while heating water7aqueous vapor or steam in another part or chamber of said retort orfurnace, and subjecting said sulfate oi' almnina to the action of saidvapor er steam until all the contained sulfuric acid is removed in adissociated form, substantially as and Vfor the purpose set forth.

The process of producing pure alumiuum oxid, \\hich consists in heatinga suitable aluminum sulfate in a suitable retort or furnace toincandescence and injectingr water, aqueous vapors or steam into saidretort or l'urnacc to act upon said incandescent sulfate thercbyseparating the acid with the impurities from said sulfate and leavingrpure aluminum oxid, said reaction being carried ou at a point above thedissociating temperature of sulfuric acid.

Si. The process ol producing acid free aluminum o.\i l. hicli consistsin subjecting aluminum suliate to heat in one part of a retort orfurnace, and heating water or steam in another part of said retort orfurnace, and conveying the resultant vapor or steam upon and throughsaid aluminum Sulfate at a uniform temperature until all the containedsulfuric acid is driven oil in a dissociated form, substantially as andfor the purpose set forth.

6. The process of producing acid `free alumina from alumina sulfurcompounds consisting in uniformly heating at an orange heat porousaluminum sulfate in the presence of water vapor until the sulfur isdriven oil'.

7. The process of producing; acid free alumina from sulfate of aluminumwhich consists in rapidly and uniformly heating anhydrous aluminumsulfate to a temperature below the tcnunerature of fusing, and passing;rsteam through the heated naiss.

S. The 'process of producing;r acid free aluminum oxid which consistsin. uniformly heating porous aluminum sulfate to above SOO degrees centigrade but below the fusing temperature and passing steam through saidmass.

GUSTAVE SCHVAHN.

lV itnesses H. I". D. SCHWAHN,

EDWARD W. lVEsT, Jr

